Yamaha DRX-2 Service Manual Download

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DRX-2

103

The processing of audio is always done in stereo (e.g.
separate left- and right-channel) and the complete
switching is realized by using HEF4052, which is a dual
four-to-one multiplexer. In principle there are three
independent selectors:

a) Scart 1-Output-Path:
Pos [7504] is used to select either Scart 2-Input (“AIN2L”/
”AIN2R”) or the signal directly from the audio DAC [7004]
(“ALDAC”/”ARDAC”) as the output source for Scart 1
(“AOUT1L”/”AOUT1R”).

The control is done by means of the lines “ASC1S” coming
from [7408] (IC [7408] acts as a port expander for the CC-
P) and “IASC1M”, which is directly coming from the CC.
Pos [7412] is used for level adaptation (3V3 to 5V) for the
“IASC1M”-signal.

b) Scart 2-Output-Path:
Pos [7503] selects between Scart 1-Input (“AIN1L”/
”AIN1R”), signals from the internal frontend (“AFEL”/
”AFER”) via MSP [7600] or audio directly from the DAC
[7004] (“ALDAC”/”ARDAC”). The outputs of this switch are
routed to Scart 2 (“AOUT2L”/AOUT2R”). This switch is
controlled via “VSA1”-and “VSA2”-line. These lines come
from [7408] that is acting as a port expander for the CC-P.

c) Record-Path:
Pos [7501] selects either signals from Scart 1 (“AIN1L”/
”AIN1R”) or Scart 2 (“AIN2L”/”AIN2R”) or Cinch-Front
(“AINFL”/ ”AINFR”) or the MSP [7600] (“AFEL”/”AFER”)
and routes to the audio ADC [7007] (“ALADC”/”ARADC”)
for record purposes.

The switch is controlled via “RSA1”- and “RSA2”-signals.

These signals come from the MSP [7600], which acts as a
port expander of the CC-P. As there can also exist a fifth
input in case of DV-In is present the corresponding analog
audio signals from the DVIO-board are firstly routed via
extra cable and connector [1960] to the MSP. The MSP
acts as a preselector between audio from internal frontend
or the DV-Input.

Each of these three selectors ([7501], [7503]&[7504])hasa
separate Op-Amp on the output for level-adaptation-,
performance- and line-driving-reasons. [7505-A & -B] for
record, [7502-C & -D] for Scart 1-Output and [7502-A & -B]
respectively for Scart 2. Every audio output line on the two
Scart connectors can be “killed” (muted) by an extra
transistors ([7506], [7508], [7509]&[7511]), which can be
activated by the “AKILL”-line. This signal is generated by
the circuit around [7404]/[7421] and is a combination of
the “KILL”- from the CC-P and the “IPFAIL” of the power-
supply-unit.

d) Line-Out-Path:
see chapter 3.5

e) Digital Audio Output-Path without IOE-Print:
Additionally to analog audio the set is also equipped with a
digital output via cinch plug [1951]. The signal is
generated on the dig. board and routed via audio interface
cable and connector [1900] to the Ana-PCB. Here the
“DAOUT”-line first passes a 6-fold inverter [7580] being
used as a driver and for performance reasons (noise
reduction, jitter, etc.). Afterwards a transformer [5580] is
necessary to achieve the correct level and also to have a
floating output with isolated ground before the signal is fed
via [3580] to cinch plug [1951]. The capacitor [2580]
performs an AC-coupling between connector- and set-
ground.

f) Digital Audio Output-Path with IOE-Print:
In case of usage of the IOE-print the digital audio signals
(input and output) are directly routed from digital board via
interface cable to plug[1920] on the IOE-print. The
“DAOUT”-line is splitted into two signals, one for cinch out
and one for optical out. The signal to cinch out first passes
a 5-fold inverter [7250] being used as a driver and for
performance reasons (noise reduction, jitter, etc.).
Afterwards a transformer [5250] is necessary to achieve
the correct level and also to have a floating output with
isolated ground before the signal is fed via [3259] to the
cinch plug [1925] (or [1926-B] in case of option “DIGITAL
IN”). The capacitors [2256] and [2266] perform an AC-
coupling between connector- and set-ground. The second
“DAOUT”-signal is fed directly via [3264] to the optical out
transmitter [6255].

g) Digital Audio Input-Path with IOE-Print:
There are two possibilities for a digital audio input signal in
case of option “DIGITAL IN”. One is the signal from the
optical receiver [6259], which is routed via [3269] directly
to plug [1920]. The second is the signal from the cinch plug
[1926-A].

This signal then passes an inverting amplifier [7250-6] and
is then routed via [2253] to the plug [1920].

3.5 Audio ADC/DAC

a) PCBs with AD1852 [7004]:
The conversion of analog audio signals from the record-
selector [7501] in the I/O (“ALADC”- & “ARADC”) is done
via UDA1361TS [7007]. This IC can process input signals
up to 2Vrms by using external resistors [3047], [3053] in
series to the input pins. As the level from the DVIO-Board
is only 1Vrms a 6dB step can be performed by setting pin 7
of [7007] to 3,3V via [7008] and the “PWONSW”-line
controlled by the CC-P to use the whole dynamic range of
the ADC. All required clock signals are generated on the
dig. board and only the audio data (“A_DAT”-line) are
routed from Ana- to Dig.-PCB for further processing.

The transformation of dig. audio back into the analog
domain is done by AD1852 [7004]. All necessary clock
signals are coming from the dig. board and dig. audio data
(“D_DATA0”-line) are converted into analog signals, which